A novel electrochemical aptasensor for detection of aflatoxin M based on target-induced immobilization of gold nanoparticles on the surface of electrode.

In this study, a novel electrochemical aptasensor was developed for detection of AFM aflatoxin M (AFM) based on the hairpin-shaped structure of AFM aptamer (Apt), gold nanoparticles (AuNPs) and complementary strand of the aptamer (CS). The conformational change of hairpin structure of Apt in the presence and absence of AFM and also negatively charged AuNPs allowed detection of AFM with high sensitivity and selectivity. In the absence of the AFM, the hairpin structure of the Apt was intact. So, a weak peak current was obtained. However, addition of AFM could disassemble the hairpin structure of the Apt. Thus, the CS-modified AuNPs came to close proximity of the surface of electrode and a strong current signal was recorded upon the addition of methylene blue as redox agent. The aptasensor allowed determination of AFM with a detection limit of 0.9 ng/L. Finally, the aptasensor was successfully applied for detection of AFM in real samples, including milk and serum samples.